U.S. patent application number 10/287959 was filed with the patent office on 2003-08-07 for process for implementation of a redundant switched full-duplex ethernet type communication network.
Invention is credited to Almeida, Philippe, Gambardella, Eddie, Lopez, Juan, Pasquier, Bruno, Portes, Dominique, Saint Etienne, Jean-Francois.
Application Number | 20030147377 10/287959 |
Document ID | / |
Family ID | 8869058 |
Filed Date | 2003-08-07 |
United States Patent
Application |
20030147377 |
Kind Code |
A1 |
Saint Etienne, Jean-Francois ;
et al. |
August 7, 2003 |
Process for implementation of a redundant switched full-duplex
ethernet type communication network
Abstract
The invention relates to a process for implementation of a
redundant switched full-duplex Ethernet type communication network
comprising at least two independent elementary networks, each
elementary network (RE1, RE2) comprising at least one source
subscriber equipment and at least one destination subscriber
equipment, connected to each other through at least one physical
link through at least one switch, each equipment being connected to
each of these elementary networks (RE1, RE2) in which a frame by
frame redundancy is made on each elementary network.
Inventors: |
Saint Etienne, Jean-Francois;
(Cugnaux, FR) ; Lopez, Juan; (Toulouse, FR)
; Portes, Dominique; (Auzeville-Tolosane, FR) ;
Gambardella, Eddie; (Blagnac, FR) ; Pasquier,
Bruno; (Thil, FR) ; Almeida, Philippe;
(Cugnaux, FR) |
Correspondence
Address: |
Robert E. Krebs
Thelen REid & Priest LLP
P.O. Box 640640
San Jose
CA
95164-0640
US
|
Family ID: |
8869058 |
Appl. No.: |
10/287959 |
Filed: |
November 4, 2002 |
Current U.S.
Class: |
370/351 |
Current CPC
Class: |
H04L 49/552 20130101;
H04L 69/40 20130101; H04L 49/351 20130101 |
Class at
Publication: |
370/351 |
International
Class: |
H04L 012/28 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 5, 2001 |
FR |
01 14264 |
Claims
1. Process for implementation of a redundant switched full-duplex
Ethernet type communication network comprising at least two
independent elementary networks, each elementary network (RE1, RE2)
comprising at least one source subscriber equipment (13) and at
least one destination subscriber equipment (14), connected to each
other through at least one physical link through at least one
switch, each equipment being connected to each of these elementary
networks, characterized in that a frame by frame redundancy is made
on each elementary network.
2. Process according to claim 1, in which there are two elementary
networks.
3. Process according to claim 1, which comprises the following
steps in transmission: addition of a numbering field in each
transmitted frame, to insert a frame number, send this frame on
each of the elementary networks (RE1, RE2).
4. Process according to claim 3, that comprises the following three
steps in reception: storage of the received frame number acceptance
of this frame only if its number has not already been received.
5. Process according to claim 4, in which the step to accept a
frame takes place within a given time window.
6. Process according to claim 4, in which the virtual link (VL)
concept is used, which is a conceptual view of a link from a source
equipment (13) to at least one destination equipment (14).
7. Process according to claim 6, in which a virtual link number is
accepted in the numbering field.
8. Process according to claim 6, in which a virtual link (VL) is
characterized by: a transfer direction, the virtual link being
single directional, a source equipment (13), one or several items
of destination equipment (14), a fixed passband, a maximum
guaranteed time for transfer of packets from a source equipment
(13) to a destination equipment, a fixed path on the network, a
unique identifier.
9. Process according to any one of the previous claims that is used
for implementation of a redundant switched full-duplex Ethernet
type communication network in avionics.
Description
TECHNICAL FIELD
[0001] This invention relates to a process for implementation of a
redundant switched full-duplex Ethernet type communication network,
particularly in avionics.
STATE OF PRIOR ART
[0002] The Ethernet network, which is the reference in the world of
communication networks, can be used to send data in digital form by
packets or "frames", where a frame is defined as being a set of
data sent in a single step on the network.
[0003] In an Ethernet network, the data in each frame are not
interpreted. The network carries the data without understanding
their meaning. A frame is composed of two types of data, network
data that are used to route the frame to its correct destination,
and useful data which comprise the "useful load" in the frame.
[0004] An Ethernet network is composed of different equipment that
is subscribed to the network, and connected to each other through a
communication means formed of active equipment called switches,
which perform three functions:
[0005] connect network subscribers in point to point mode through
physical links, which are physical supports for messages to be
exchanged, for example twisted pair cables,
[0006] route (switch) frames sent by source equipment to one or
more destination equipment,
[0007] check the integrity and the format of the Ethernet
frame.
[0008] FIG. 1 illustrates an Ethernet network composed of two
switches 11 interconnected to each other and each connected to
three items of subscriber equipment 12 in point to point mode.
[0009] Operation of such a network is simple. Each network
subscriber can send frames in digital form at any time towards one
or several other subscribers. When a switch receives the frames,
the "network information" data are analyzed to determine the
destination equipment. The frames are then switched towards this
equipment.
[0010] In the "switched full-duplex Ethernet type network"
expression:
[0011] the "full-duplex" term means that the subscriber can send
and receive frames at the same time on the same link,
[0012] the "switched" term means that the frames are switched in
switches on appropriate outputs.
[0013] For example, this network may be a 100 Mbits/s switched full
duplex type network on twisted pair; the term "twisted pair" means
that connections between the equipment and the switches are
composed of two pairs of cables, each pair being twisted; the term
100 Mbits/s simply means the transmission or reception speed of
frames on the network.
[0014] The Ethernet technology imposes:
[0015] a minimum size and a maximum size on the frames,
[0016] an identification of the source and/or the destination(s) in
each frame,
[0017] a CRC ("Cyclic Redundancy Check") that checks the integrity
of the transported data.
[0018] At the present time, in the civil aeronautics field, data
exchanges between the various onboard computers are based on the
use of the ARINC 429 aeronautical standard.
[0019] However, the switched full-duplex Ethernet network is
frequently used in industry. The emergence of new communication
technologies shows that this type of network is an open and
standard solution (IEEE standard 802.3) with a considerable
potential for development as a local network. But this type of
solution does not provide any means of guaranteeing segregation and
transfer performances (in terms of throughput, latency, etc.)
necessary for avionics applications.
[0020] The purpose of this invention is to improve the availability
of such a network, by providing means of protecting against the
loss of a link or a switch, to enable its use in avionics.
[0021] In general, in a distributed control system, the
communication system is made redundant so that each node in a set
of nodes (equipment) can be controlled from one of these nodes, and
so that these nodes can be connected so as to increase the load
factor on the system and therefore its efficiency.
[0022] A European patent application EP-0 854 610 describes an
Ethernet communication redundancy process between a set of nodes
forming such a distributed control system. These nodes are
connected to each other in duplex through communication lines in a
first and a second Ethernet networks, that are independent from
each other. At the transmission end, a first node transmits
identical data on communication lines in the first and the second
networks, a data identifier being added to the transmitted data. A
second node at the reception end determines which of the identical
data received from the first node through communication lines in
the first and the second networks arrived first and uses it as the
reception data. The second data are then rejected if they are
identical to the first data.
[0023] Unlike the process described in this patent application
which is applicable to data, the purpose of the invention is to
make a process enabling frame by frame redundancy.
PURPOSE OF THE INVENTION
[0024] The invention relates to a process for implementation of a
redundant switched full-duplex Ethernet type communication network
comprising at least two independent elementary networks, each
comprising at least one source subscriber equipment and at least
one destination subscriber equipment, connected to each other
through at least one physical link and through at least one switch,
each equipment being connected to each elementary network, in which
a frame by frame redundancy is made on each elementary network.
[0025] This process comprises the following steps in
transmission:
[0026] addition of a numbering field in each transmitted frame, to
insert a frame number,
[0027] send this frame on each of the elementary networks.
[0028] It includes the following steps on reception:
[0029] storage of the received frame number,
[0030] acceptance of this frame only if its number has not already
been received.
[0031] Advantageously, the step for acceptance of a frame takes
place during a given time window.
[0032] In one advantageously embodiment, the virtual link concept
is used, which is a conceptual view of a link from one source
equipment to at least one destination equipment. A virtual link
number is accepted in the numbering field of each transmitted
frame. A virtual link is characterized by:
[0033] a transfer direction, the virtual link being single
directional,
[0034] a source equipment,
[0035] one or several items of destination equipment,
[0036] a fixed passband,
[0037] a maximum guaranteed time for transfer of packets from a
source equipment to a destination equipment,
[0038] a path fixed on the network,
[0039] a unique identifier.
[0040] Advantageously, the process according to the invention can
be used for the implementation of a redundant switched full-duplex
Ethernet type communication network in avionics.
[0041] This type of network redundancy, which may for example
consist of doubling up the network, with each subscriber being
connected to each of the two networks, one of the two packets being
selected on reception, can increase the network availability; the
network will continue to operate if it has one or several defective
switches or links.
[0042] The invention can achieve redundancies of order 2 or more,
independently of the communication stack and applications.
BRIEF DESCRIPTION OF THE FIGURES
[0043] FIG. 1 illustrates an Ethernet network according to known
art,
[0044] FIG. 2 illustrates the concept of a virtual link in an
Ethernet network according to known art,
[0045] FIG. 3 illustrates an Ethernet network according to known
art in which several virtual links are shown,
[0046] FIG. 4 illustrates services used in the process according to
the invention,
[0047] FIG. 5 illustrates an example of second order redundancy in
subscribed equipment according to the invention,
[0048] FIGS. 6A and 6B illustrate operation of the process
according to the invention in transmission mode and in reception
mode respectively.
DETAILED DESCRIPTION OF EMBODIMENTS
[0049] The invention relates to a process for the implementation of
a redundant switched full-duplex Ethernet type communication
network comprising at least 2 elementary networks each of which
comprises at least one source subscriber equipment and at least one
destination subscriber equipment connected to each other through at
least one physical link. In the reminder of the description, we
will consider two elementary networks RE1 and RE2 as a
non-limitative example. This process makes a frame by frame
redundancy on each of the elementary networks.
[0050] In transmission, it comprises the following steps:
[0051] addition of a numbering field in each transmitted frame, to
insert a frame number so that each frame can be identified in
time,
[0052] send this frame on each of the elementary networks.
[0053] In reception, it comprises the following steps:
[0054] storage of the received frame number,
[0055] acceptance of this frame only if its number has not already
been received.
[0056] Advantageously, the frame acceptance step only takes place
during a given time window, so that only a limited memory size can
be used, each frame number reappearing after a determined time.
[0057] Therefore, the process according to the invention only sends
the first frame received from an elementary network, to the
application considered, the other corresponding frames from other
elementary networks being rejected.
[0058] FIG. 5 illustrates an example of a second order redundancy
used in a subscriber equipment.
[0059] In one advantageous embodiment, the process according to the
invention uses the virtual link concept to limit the end to end
transfer time, in other words source equipment towards one or
several destination equipment.
[0060] This virtual link (VL) concept provides means of isolating
data transfers between a source equipment 13 and destination
equipment 14. A virtual link VL is seen as a "pipe" on the network,
as illustrated in FIG. 2.
[0061] A virtual link VL is characterized by:
[0062] a transfer direction, the virtual link being single
directional,
[0063] a single source equipment 13,
[0064] one or several destination equipment 14,
[0065] a fixed passband (maximum number of packets and their size
per second),
[0066] a maximum guaranteed time for transfer of packets from a
source equipment 13 to a destination equipment 14, regardless of
the behavior of the rest of the network, each virtual link having
its own transfer time,
[0067] a path fixed on the network,
[0068] a unique identifier.
[0069] A network subscriber may comprise several virtual links VL1,
VL2, VL3, as shown in FIG. 3. We have:
[0070] a virtual link VL1 from equipment 21 to equipment 23, 24 and
25,
[0071] a virtual link VL2 from equipment 21 to equipment 22 and
23,
[0072] a virtual link VL3 from equipment 23 to equipment 22,
[0073] When equipment 21 wants to send a packet to equipment 23, 24
and 25, it sends a packet on the virtual link VL1. When it wants to
send a packet to equipment 22 and 23, it sends a packet on the
virtual link VL2.
[0074] The difference between virtual links VL1 and VL2 is
identified by the destination identifier in the packet. On the
network, the virtual link to which a packet belongs is determined
by the identifier of the virtual link in the packet.
[0075] A switch uses a static configuration table to determine the
virtual links that it is required to switch, and the allowable
number of packets for a virtual link.
[0076] The virtual link concept is a means of fixing communications
between equipment by configuring routes and passbands allocated to
the virtual links. Thus, the flow formed by a virtual link is sure
to be not disturbed by other flows sharing the same physical links
all along its route in the network.
[0077] Furthermore, the virtual link concept enables central flow
management, to make sure that the sum of the passbands allocated to
virtual links on the same physical link does not exceed the
capacities of the technology of this physical link. In the above
example, the sum of the passbands of virtual links VL1 and VL2 must
be less than the transmission capacity of the physical link from
equipment 21.
[0078] Therefore, a virtual link is a conceptual representation of
a link from a transmitter equipment to one or several items of
receiver equipment that have the following characteristics:
[0079] fixed and predetermined route on the network,
[0080] fixed and guaranteed passband,
[0081] maximum guaranteed end to end latency
[0082] explicit identification in a multidestination or "multicast"
type Ethernet frame (multidestination MAC address) and this
identification is kept when passing through one or more
switches.
[0083] As illustrated in FIG. 4, the process according to the
invention is then characterized by the implementation of several
services in each subscriber equipment 50:
[0084] a transmission service, the role of which is to enable an
application 52 to access virtual links in transmission (virtual
links VL1 and VL2). This service multiplexes virtual links towards
a physical link through an Ethernet interface, and for each virtual
link sends packets as a function of the passband allocated to the
virtual link.
[0085] A reception service 55 that decodes frames (virtual links
VL21 and VL22), checks their format and makes useful data available
to applications.
[0086] In these transmission and reception services, the
application may treat a virtual link like a queue.
[0087] Other protection services help to guard against some network
failures:
[0088] A service for protection of a passband in the switch, which
for each incoming virtual link is capable of checking the time
characteristics of packets (spacing between packets, the consumed
passband). If the allowable characteristics are exceeded, the
packets are simply destroyed to prevent a failure in a transmitter
or a virtual link from adversely affecting traffic in other virtual
links starting from this switch.
[0089] A subscriber network redundancy service 60 that sends and
receives each frame on the two elementary networks RE1 and RE2, in
order to implement network redundancy. This network duplication in
two elementary networks RE1 and RE2, that is transparent for
applications, provides a means of guarding against a failure in a
switch or an interface (it does not replace system level
redundancy). This network redundancy service 60 is connected to at
least one first Ethernet interface 61 with the elementary network
RE1, and a second Ethernet interface 62 with the elementary network
RE2.
[0090] As shown in FIG. 5, the equipment in the process according
to the invention to obtain redundancy of virtual links on the
physical layer comprises at least two physical interfaces, so that
they can be connected to at least two independent elementary
networks RE1 and RE2. Their communication stacks include redundancy
mechanisms that enable:
[0091] sending an identical frame on the elementary networks RE1
and RE2,
[0092] selecting the first valid received frame.
[0093] Therefore, in this embodiment, the steps in the process
according to the invention used in the subscriber equipment and
applied by a virtual link onto the network are such that:
[0094] in transmission, for each frame received from the
communication stack:
[0095] a numbering field is added so that a counter numbers the
frame corresponding to each virtual link,
[0096] this frame is sent onto the elementary networks RE1 and
RE2.
[0097] in reception, for each frame assigned to a virtual link:
[0098] the frame number is stored,
[0099] this frame is accepted if this number has not already been
received, and if it is received it is destroyed.
[0100] FIG. 6A illustrates this embodiment of the process according
to the invention in transmission, and 6B illustrates it in
reception.
[0101] FIG. 6A illustrates the following in sequence:
[0102] addition of a numbering field on the IP/UDP/data
assembly,
[0103] numbering of the frame for each virtual link,
[0104] send the frame to each Ethernet controller that formats it
as an IEEE 802.3 frame.
[0105] Numbering is done by virtual link, and the same number can
be used for two different virtual links.
[0106] FIG. 6B shows the following in sequence:
[0107] for each virtual link, verification of the number in the
numbering field,
[0108] the frame is eliminated if the number has already been
received,
[0109] otherwise the frame is sent to the higher layer.
[0110] The counter field can be small, and when the counter reaches
its maximum value, frame numbering restarts from zero.
* * * * *